A web browser that just prints "Done" instead of the web page isn't
of much use, so we add some lines at the end of the method
handle_url to print the contents of the web page:
void handle_url(string this_url)
write("Fetching URL '" + this_url + "'...");
Query web_page = get_url(this_url);
if(web_page == 0)
write("This is the contents of '" + this_url + "':\n\n");
string page_contents = web_page->data();
write(page_contents + "\n");
} // handle_url
The interesting part here is the expression
where we call the method data in the data item
web_page. This method returns the contents of the web page,
i. e. the HTML code, as a string. We then print that string.
Methods in data items?
"But", you say, "what is all this about a method in a data item? I
thought methods were pieces of code that were parts of a program?"
Well, a method is a part of a program, just as we have seen.
But just as the web browser we have written contains methods, other
programs can contain methods. And the "data type"
Protocols.HTTP.Query is actually another program. The big
difference is that it doesn't have a method called main, so
it can't be used by itself. It can only be used as a part of another
program, as we have done here.
Somewhere on your computer there is a file, called something like
This file contains the program Query with all its methods and
variables, among them the method data.
A program like Query, which can be used in other programs
in the way we have seen, is often called a class. You can read
more about how to use, and create, classes in the chapter about